1. Technical Field
The embodiments herein generally relate to an electrical power supply device and particularly to controllers used for domestic and industrial purposes. The embodiments herein more specifically relate to the switching devices such as miniature circuit breaker, residual current circuit breaker, isolator and their auxiliary contacts, etc.
2. Description of the Related Art
Electrical switching devices are used to protect the electrical circuitry and equipment from the damage due to an abnormal condition, such as an overload condition, a relatively high level short circuit or a fault condition. The electrical switching devices typically have two operating handle positions corresponding to the status of the separable contacts. For example, these positions include an ON position, in which the separable contacts are closed and an OFF position in which the contacts are open. Some switching devices have a third position which corresponds to a tripped condition in which the contacts are tripped open.
Switching devices are usually installed in an enclosure so that the entire control and distribution network arranged in the form of metallic sheets and/or cable wires are housed inside the enclosure. All the operating means are arranged outside the enclosure to prevent an access to the high voltage sections to eliminate the generation of a potential hazard. It is often desirable or essential that the settings of the switching devices remain undisturbed in the switching device during a maintenance operation. Unauthorized or inadvertent changing of the position of these breakers could result in unwanted interruptions to service or operations and serious damage to an electrical apparatus, or even serious harm to a person. For example, accidental actuation of a circuit breaker might result in electrocution or shock to a workman performing electrical work or repair on equipment downstream from the circuit breaker.
Therefore enough safety measures must be taken to prevent another person from inadvertently returning the circuit breaker handle to the ON position, when a worker is doing electrical work in an area other than the immediate vicinity of the circuit breaker box or electrical panel. One such safety measure is the addition of a locking assembly to the switching device to prevent the displacement of the circuit breaker operating handle.
A circuit breaker is an automatically-operated electrical switch designed to protect an electrical circuit from damage caused by overload or short circuit. Unlike a fuse, which operates once and then has to be replaced, a circuit breaker can be reset (either manually or automatically) to resume normal operation. Circuit breakers are made in varying sizes, from small devices that protect an individual household appliance up to large switchgear designed to protect high voltage circuits feeding an entire city. The Circuit breakers for larger currents are usually arranged with pilot devices to sense a fault current and to operate the trip opening mechanism.
There are different technologies used in circuit breakers and they do not always fall into distinct categories. The commonly used circuit breakers in domestic, commercial and light industrial applications at low voltages (less than 1000 V) include a Miniature Circuit Breaker (MCB) and a Moulded Case Circuit Breaker (MCCB).
The MCB is used for a rated current of not more than 100 A. the trip characteristics are not adjustable normally. The MCB employs thermal or thermo-magnetic principles. The MCCB is used for a rated current up to 1000 A. The MCCB uses the thermal or thermal-magnetic operation. The trip current may be adjusted in the MCCB.
In any kind of circuit breaker or switching device the operating mechanism plays a main role. Since the module width of the low voltage circuit breaker is very less (17.5 mm), the operating mechanism should be compact. Moreover, since a rotary contact is used in the circuit breakers, some special mechanism needs to be devised to make and break the contacts quickly and safely.
The currently available circuit breaker utilizes several linkages to operate a trip mechanism to make and break the electrical contacts. The circuit breakers used in low voltage applications are mostly used for domestic purposes. None of the currently available circuit breaker or switching device has a compact operating mechanism and has less operating time to make and break the electrical contacts quickly and safely. Hence there is a space constraint and a compelling need for the space saving type circuit breaker.